ESQL: Reenable test a HeapAttack test (#134502)

We've added a bunch more memory tracking since this was muted and it
doesn't reproduce locally.

Closes #128720

Author: nik9000

muted-tests.yml

@@ -375,9 +375,6 @@ tests:
 - class: org.elasticsearch.packaging.test.DockerTests
   method: test072RunEsAsDifferentUserAndGroup
   issue: https://github.com/elastic/elasticsearch/issues/131412
-- class: org.elasticsearch.xpack.esql.heap_attack.HeapAttackIT
-  method: testLookupExplosionNoFetch
-  issue: https://github.com/elastic/elasticsearch/issues/128720
 - class: org.elasticsearch.packaging.test.DockerTests
   method: test050BasicApiTests
   issue: https://github.com/elastic/elasticsearch/issues/120911